Question

Explain why Intelligent Design proponents believe the bacterial flagellum supports their theory, and how the mouse trap demonstration refutes that theory.

Answer 1

evolutionary biology is replete with explanations for complex biological structures, scientists concerned about evolution education have been forced to confront “intelligent design” (ID), which rejects a natural origin for biological complexity

in recent yearsscientists have been forced to confront a resurgence of opposition to evolution in the political realm of public education. This new antievolutionism is called “intelligent design” (ID). Its proponents allege that it is a revolutionary new scientific explanation for complex adaptations, that it is purely secular and definitely not creationism, and that it is therefore pedagogically and legally appropriate for public school biology classrooms. However, an analysis of ID shows that in both content and history, it is a subset of an earlier antievolution movement known as creation science.

Dembski's “design inference” resembles Behe's ID criterion, but Dembski's arguments tend to be conducted at a high level of abstraction, ornamented with mathematical notation of dubious utility. In brief, Dembski contends that if a given event or object has a low probability of occurrence on all of the nondesign hypotheses available, then it exhibits what he calls specified complexity; specified complexity is, he argues, a reliable indicator of design. The only biological structure to which Dembski attempts to apply his method is the bacterial flagellum (16). Noting that the chance of its parts assembling at random is astronomically low, and relying on Behe's argument to exclude gradual evolutionary assembly, Dembski concludes that it was intelligently designed. Like Behe, however, he asserts that science is incapable of proceeding further to determine the nature of the designer or the means by which the design was instantiated.

The design inference and irreducible complexity consist of two components: an extensive negative argument against the plausibility of evolutionary explanations, and then a brief attempt at a positive argument relying on an analogy between biological adaptations and human artifacts. Behe's negative argument against stepwise assembly of “irreducible” systems fails because it mistakenly assumes that evolution proceeds only by improvement of an extant function, whereas evolutionary theory extending back to Darwin has always emphasized the importance of changes of function in the origin of complex adaptations (17–22). The flagellum, although elucidated long after Darwin, is a useful case to examine. Contrary to the assertions of Behe and Dembski, a survey has shown that only 20 of the 42 proteins of the Salmonella typhimurium flagellum are universally required in bacterial flagella; and of those, 18 have already been found to have homologous related proteins that function in other, simpler biochemical systems (23). It is therefore not true that simpler precursors would be nonfunctional; they clearly could have had different functions, just like the related systems in existence today. Deleting parts from a modern system does not simulate evolution in reverse, any more than decapitating modern vertebrates provides information about the origin of cephalization in early invertebrates.

Behe uses the mousetrap as an illustrative example of this concept. A mousetrap consists of five interacting pieces: the base, the catch, the spring, the hammer, and the hold-down bar. All of these must be in place for the mousetrap to work, as the removal of any one piece destroys the function of the mousetrap. Likewise, he asserts that biological systems require multiple parts working together in order to function. Intelligent design advocates claim that natural selection could not create from scratch those systems for which science is currently unable to find a viable evolutionary pathway of successive, slight modifications, because the selectable function is only present when all parts are assembled.The mousetrap is not irreducibly complex after all.In his 2008 book Only A Theory, biologist Kenneth R. Miller challenges Behe's claim that the mousetrap is irreducibly complex.[53] Miller observes that various subsets of the five components can be devised to form cooperative units, ones that have different functions from the mousetrap and so, in biological terms, could form functional spandrels before being adapted to the new function of catching mice

Other systems identified by Miller that include mousetrap components include the following:[53]

• use the spitball launcher as a tie clip (same three-part system with different function)
• remove the spring from the spitball launcher/tie clip to create a two-part key chain (base + hammer)
• glue the spitball launcher/tie clip to a sheet of wood to create a clipboard (launcher + glue + wood)
• remove the hold-down bar for use as a toothpick (single element system)

The point of the reduction is that - in biology - most or all of the components were already at hand, by the time it became necessary to build a mousetrap. As such, it required far fewer steps to develop a mousetrap than to design all the components from scratch.

Thus, the development of the mousetrap, said to consist of five different parts which had no function on their own, has been reduced to one step: the assembly from parts that are already present, performing other functions.

In their continuing efforts to make a case for the "intelligent design" of biochemical systems, Michael Behe and others have compared such systems to mousetraps. By invoking an ordinary object like the mousetrap, they hope to explain their concept of "irreducible complexity" in terms that people can easily grasp. Here's an example of how this comparison is made:

"A good example of such a system is a mechanical mousetrap. ... The mousetrap depends critically on the presence of all five it its components; if there were no spring, the mouse would not be pinned to the base; if there were no platform, the other pieces would fall apart; and so on. The function of the mousetrap requires all the pieces: you cannot catch a few mice with just a platform, add a spring and catch a few more mice, add a holding bar and catch a few more, All of the components have to be in place before any mice are caught. Thus the mousetrap is irreducibly complex